My 12 yr old has always been ahead in her physical development and currently looks about 15. However, emotionally I would say she is younger than her years.
Last night she asked me when I lost my virginity as she "...didn't want to do it too early or too late..." 
I tried not to look too shocked and told her that I was 16 but that it was a very big step and should only be taken when in a loving relationship, certainly not to be entered into lightly etc.
How have others handled this subject. I don't want to come down too authoritarian as i do want her to talk to me about these things but I don't want to be too liberal either!
Thinking of sex at 12! I think I was still playing with Barbies!